In Korean patent application No. 10-2006-0113329, filed on Nov. 16, 2006 by the same applicant of the present invention, i.e., Electronics and Telecommunications Research Institution (ETRI), “a human body communication system by using limited passband and a method thereof” is suggested. In the above patent application, limited passband, i.e., from 5 MHz to 40 MHz, is used to implement the human body communication system, and a scrambling based on a unique user identification (ID), a channel coding, an interleaving and a spreading operate in order to perform a low-power and a stable human body communication.
However, the above patent application uses the passband having an intermediate frequency (fc), which is used in most of communication systems. Consequently, an analog transceiver including a digital-to-analog converter, an analog-to-digital converter and an intermediate frequency converter is needed. An aspect of low-power, the above converters are considered undesirably. Moreover, in the above patent application, a time domain/frequency domain spreading method is applied to obtain a processing gain, but the spreading method is not efficient for increasing data transmission rate and performing transmission/reception data stably due to the limited frequency band.